Agriculture Reference
In-Depth Information
individual. The limits of the classes were not well deÝned, thus there was much latitude for soil
scientists to make classiÝcation decisions, based on their judgment as to the degree of similarity
to one central concept as opposed to another. Soil Taxonomy put a greater focus on observable and
measurable class limits deÝning diagnostic horizons, features, and other differentiating character-
istics. This shift from a qualitative to a quantitative emphasis had several practical effects.
Parity and Consistency in Classifying Soils
The use of Soil Taxonomy has effectively placed all soil scientists on an equal footing with
regard to their ability to classify a soil. Smith (1963) explained that the choice of differentiating
criteria was intended to group soils with similar genesis, but genesis itself was not in the deÝnitions.
Instead, it was one step removed from the deÝnitions. This allowed soil scientists to focus on soil
properties, and to classify soils rather than processes. This leveled the playing Ýeld for all soil
scientists, regardless of status within the NCSS Program. No longer did one have to theorize about
the genesis of the soil in order to classify it, something that must have been a serious problem
when there were either competing theories regarding a soilÔs genesis, or when the genesis was
simply not known by those attempting to classify the soil. With a good morphological description
and key laboratory data, a junior Ýeld soil scientist was on equal footing with the most senior
correlator. As a result, Soil Taxonomy could be applied universally and consistently by any com-
petent soil scientist.
Quantity and Quality of Data Collection
The attention of Ýeld scientists became focused on those characteristics selected as class
differentiae, thus inÞuencing the kind of information being recorded. It increased the quantity and
quality of data gathering by encouraging the recording of greater detail in soil descriptions, and
by encouraging laboratory analyses to document properties not readily observable in the Ýeld but
required for determining taxonomic placement. The kind of information obtained was directly
inÞuenced by the need to determine the presence of diagnostic horizons and features, and to
document other differentiating characteristics used as class limits. A potential downside to this
focus on the properties used as differentiae was recorded in the report of the committee on the
ÑNew Soil ClassiÝcation SystemÒ to the 1963 NCSS National Work Planning Conference (Soil
Survey Division, 1999, p. 27Ï28). Guy Smith is reported as commenting
As Dr. Simonson has pointed out again and again, it is possible to become a prisoner of oneÔs
classiÝcation. The differentiae that are used in the 7
Approximation will get very great emphasis
and those that have not been used can easily be overlooked. Yet, in deÝning a soil, one must think of
all of its properties and not just the ones that have been used in differentiae. We have been able to
use only a very few soil properties to deÝne our taxa. Soils have a great many other properties, and
we must be on our guard to be sure that these others, which actually may be more important from
some viewpoints than those we have used, do not get overlooked.
th
This caution is as valid today as it was then. As observers of soils, we tend to see what we are
taught to see, and may not strive to observe more once we know enough to complete the task of
classifying a soil. When the need for change in the system is recognized, however, adding or
changing differentiae at the higher categories can be (and has been) done, but it requires that a
proposal be developed, reviewed widely, and approved, and this can take considerable time.
However, at the series level of classiÝcation, there are no predetermined differentiating properties,
allowing considerable freedom to deÝne a series based on virtually any soil property observed
within the series control section. This approach, however, is only useful for separating soils that
the classiÝcation system has grouped into the same family. It cannot be used to group soils that
taxonomy has set apart at a higher level.
